The treatment of blood or similarly perishable liquids by means of dialysis is well known. Typically, apparatus for such treatment comprises a dialyzer in combination with a closed circulating system for circulating a treatment liquid through the dialyzer to thereby effect dialysis of the blood. The closed system normally includes means for heating the treatment liquid to a temperature sufficient to effect the desired treatment or purification of the blood or other perishable liquid. Further, such heating means may be operative to heat the treatment liquid to above the treatment temperature such that the treatment liquid can be used to cleanse or sterilize the system when it is not in use.
When the blood treating apparatus as above described is in use and a patient's blood circulation system is connected directly to the dialyzer, it is essential that no heating of the treatment liquid to above the treatment temperature be permitted. Therefore, in order to avoid possible actuation of the heating element to heat the treatment liquid to the higher cleaning or sterilizing temperature, various safety devices have been employed. Such devices have included micro-switches which are connected to flexible tubes which usually connect the dialyzer to the closed circulating system. However, such micro-switches have been known to be acted upon by mechanical means other than those intended to operate such switches. Therefore, assurance that the treatment liquid would not be heated to above the treatment temperature is not sufficiently assured.
It is therefore an object of the present invention to provide an apparatus for treating blood or other perishable liquids which assures that the treatment liquid will not be heated to a cleaning or sterilizing temperature while the apparatus is in use and connected to a patient, thus providing the safety which has heretofore been lacking in prior art devices.